Drawing dies



Aug. 5, 1958 Filed April 16, 1954 2 Shets-Sheet 1 FIG. 2-

a Is i \I 5 Inventor A ttorneys R. HAMPTON 2,846,056

DRAWING DIES United States Patent 1. DRAWING DIES Ronald Hampton,Wightwick, near Wolverhampton, England, assignor to Patents andInvestments Limited, Wolverhampton, England Application April 16, 1954,Serial No. 423,732

Claims priority, application Great Britain May 26, 1953 1 Claim. (Cl.205-26) This invention relates to drawing dies, that is to say, dieshaving apertures through which work-pieces are forced, either by pullingor pushing upon the work-pieces, such a die operating upon thework-piece to form the latter to a cross section corresponding to theshape of the aperture in the die. In this connection a die may be merelyreducing the dimensions of the cross sectional form of a work piece, orit may be altering the cross sectional form with or without reducing thecross sectional area of the work-piece.

The object of the present invention is to provide an improvedconstruction of die, particularly for use in cold drawing bar stock,which will be more efiicient in use than dies as hitherto constructed.

In drawing dies as hitherto constructed, a central aperture in the dieblock, of contour corresponding to the finished section to be produced,is defined by the socalled bearing surfaces of the die, and leading upto said bearing surfaces are curved surfaces known as the leads orleading surfaces, which surfaces are curved longitudinally but aretransversely parallel with the bearing surfaces.

According to the present invention, a die is provided with leadingsurfaces which are not only curved longitudinally but also have a convexcurvature in transverse direction.

An embodiment of the invention will now be described with reference tothe accompanying drawings, in which:

Figure 1 is a front elevation of a drawing die.

Figure 2 is a sectional side elevation on the line 2-2 of Figure 1.

Figure 3 is a sectional plan view on the line 3-3 of Figure 1.

Figure 4 is a sectional elevation on the line 4-4 of Figure 3.

Figure 5 is a further sectional elevation on the line 55 of Figure 3.

Referring to the drawings, the die block has a central hexagonalaperture or throat 11 defined by the six bearing surfaces 12.

The leads of leading surfaces 13 of the die are curved longitudinally,i. e., from the front face or mouth 14 of the die said leading surfaces13 are of convex curvature in rearward direction so as together toafford a converging lead toward the die throat 11. In addition to thislongitudinal curvature, the leading surfaces 13 are all formed with anarcuate convex curvature which extends in transverse direction acrossthe entire width of the leading surface with the convexity diminishinguniformly from the mouth to the throat where it merges with the sidesthereof, as is most clearly illustrated in Figures 1, 4 and 5.

The embodiment above described is an example of a die suitable for usein the production of hexagonal bar sections from raw material which ismerely closely related in section to the finished section produced bythe die.

2,846,656 Patented Aug. s, 1958 Hitherto, in the production of barsections, metal bars have been cold bright drawn from raw material whichhas-been hot rolled to a corresponding section within reasonable limitsof the finished bar section to be pro duced, the said hot rolled barsbeing then drawn through a die, constructed in the known mannerpreviously referred to, to produce the finished section, the leading andbearing surfaces of the die working the material from the hot rolledsection to a corresponding finished section of smaller dimensions.

Taking into consideration the flow of metal of the bars being worked,when the material being worked is of suitable corresponding section andof appropriate dimension relative to the finished work, it has beenfound satisfactory to employ the said known dies having the leadingsurfaces parallel with the bearing surfaces.

The present invention however, provides a die by means of which, forexample, a bar of hexagonal, septagonal,

octagonal or like polygonal section can be produced by cold drawing fromround section bar stock, or bar stock of any other closely relatedsection to the finished section which is practicable as regards thedisplacement of metal which can be effected by cold work.

This is achieved by the transverse curvature of the leading surfaces 13in accordance with the invention, the arrangement being such that littlework shall be performed upon the extreme points or corner portions ofthe section being drawn until said points or corner portions actuallymake contact with the bearing surfaces 12 of the die.

In a die as hitherto constructed such extreme points or corner portionsof the section under work, through restriction in the flow of metal,tend to fail ultimately to come into contact with the bearing surfacesof the die, so that a true and clean section is not obtained.

In a die constructed according to this invention the initial heavy workon the section being drawn is effected by the leading surfaces 13 alongthe centerlines of the surfaces of the finished section, which not onlycauses the metal to elongate and flow into its correct proportions atthe points of contact, but also causes the metal to flow laterallyoutwards to the extreme points or corner portions of the section, sincethe construction of the leading surfaces 13 alfords clearance whichallows 1 this lateral outward flow, so that when the said extreme pointsor corner portions reach the bearing surfaces 12 of the die, there is asufiiciency of metal to fill completely the die aperture 11, thisensuring a true and clean finished section. The clearance here referredto is provided in part by relating the size of the die mouth to thethroat so that a circle circumscribing the former is much greater than acircle circumscribing the latter, as will be apparent from an inspectionof the drawings.

The invention thus provides a die by means of which it is possible tomanufacture a finished section from a size of bar which is of minimumdimensions relative to the maximum dimensions of the finished section.

It will also be found expedient to use the improved die in themanufacture of bars which are to be cold bright drawn from raw materialwhich has been hot rolled to a section similar to the finished sectionto be produce-d. In the event of the hot rolled bars not being rolledfully to the extreme points or corner portions of the section, theaction of the improved die in spreading the metal toward said extremepoints or corner portions gives a satisfactory finished section.

It will be appreciated that whereas the foregoing description mentionscold bright drawing, and sections of regular polygonal form, the presentinvention is equally applicable to all sections, and also to dies forother specific uses, e. g., metal extrusion.

Having now fully described my invention, what I claim and desire tosecure by Letters Patent is:

In a die for drawing polygonal bars from metal stock, a one-piece dieblock,,a polygonal die throat in said block having sides correspondinginfnumber and size to the finished bar, a bell-shaped mouth .i'n said,die block defined by a plurality of integrally joined leading faces, onefor each side of said throat, said mouth being so related in size tosaid throat that avcircle circumscribing said mouth is much greater thana circle circumscribing said throat, each of said faces having a longi-References Cited in the file of this patent .UNITED STATES PATENTS2,012,022 Richardson Aug. 20; 1935

